The present invention relates to a quartz crystal unit, its manufacturing method and a quartz crystal oscillator.
In particular, the present invention relates to the quartz crystal unit and the quartz crystal oscillator comprising a width-extensional mode quartz crystal resonator with a new cut angle and new electrode construction which is available for wearable equipment, communication equipment, measurement apparatus and consumer products requiring miniaturization, high accuracy, shock-proof and low prices for the quartz crystal resonator.
A NS-GT cut coupling quartz crystal resonator which vibrates in the coupled width-extensional mode and length-extensional mode is well known and used as a time standard of consumer products and communication equipment. FIG. 9a and FIG. 9b show a top view and a side view of the conventional NS-GT cut coupling quartz crystal resonator. In FIGS. 9a, 9b, The resonator 200 comprises vibrational portion 201, connecting portions 203, 206 and supporting portions 204, 207. The supporting portions 204 and 207 include respective mounting portions 205 and 208.
In addition, as shown in FIG. 9a and FIG. 9b, electrodes 202 and 211 are disposed on the upper and lower faces of the vibrational portion 201, the electrode 202 extends to the mounting portion 205 through the connecting portion 203, while the electrode 211 extends to the mounting portion 208 through the connecting portion 206. The electrodes 202 and 211 have opposite electrical polarities, and two electrode terminals are constructed.
Also, as shown in FIG. 10, the resonator 200 is mounted on a pedestal 313 by conductive adhesives at the mounting portions 205 and 208. Furthermore, the pedestal 313 is connected to two lead wires 314, 315 which pass through a case 311, and the pedestal 313 with the resonator 200 is housed in a quartz crystal unit of tubular type 300 comprising the case 311 and a cap 312. Namely, the electrodes 202 and 211 are connected to the lead wires 314 and 315, respectively.
Now, when an alternating current(AC) voltage is applied between both lead wires 314 and 315, an electric field Et occurs alternately in the thickness T direction, as shown by arrow signs of the solid and broken lines in FIG. 9b. As a result, the coupled width-extensional mode and the length-extensional mode whose frequencies are inversely proportional to width W and length L of the vibrational portion, respectively, can be excited at the same time, and the NS-GT cut coupling resonator coupled in inverse phase is provided. The above-mentioned resonator is formed integrally by a chemical etching process.
In addition, the lager the area of vibrational portion for the NS-GT cut resonator becomes (low frequency), the smaller series resistance R1 becomes and the larger quality factor Q becomes. Also, the NS-GT cut resonator with excellent frequency temperature behavior is determined by a dimensional ratio W/L, and which has a value of 0.95 approximately. In order to get a frequency higher than 4 MHz, it is necessary to decrease the area of the vibrational portion for the resonator.
Recently, according to the miniaturization and weight lightness of consumer products and communication equipment with a frequency higher than 4 MHz, a miniature quartz crystal unit and a miniature quartz crystal oscillator comprising a NS-GT cut resonator with the higher frequency is also required with a small series resistance R1 and high quality factor Q.
It is, however, impossible to provide a miniature quartz crystal unit and a miniature quartz crystal oscillator having a NS-GT cut resonator with a frequency higher than about 4 MHz with a small series resistance R1 and a high quality factor Q because the area of vibrational portion for the resonator becomes very small to get the higher frequency, and more an electro-mechanical transformation efficiency becomes very small, so that a series resistance R1 becomes large and a quality factor Q also becomes small.
It is, therefore, desirable to provide a quartz crystal unit and a quartz crystal oscillator comprising a novel and miniature quartz crystal resonator with a frequency higher than about 4 MHz with a small series resistance R1, a high quality factor Q and a zero temperature coefficient.
The present invention relates to a quartz crystal unit, its manufacturing method and a quartz crystal oscillator, In addition, the quartz crystal unit and the quartz crystal oscillator comprise a width-extensional mode quartz crystal resonator capable of vibrating in a single mode with a high electro-mechanical transformation efficiency and a zero temperature coefficient.
In particular, the present invention relates to the quartz crystal unit and the quartz crystal oscillator comprising the width-extensional mode quartz crystal resonator with a new cutting angle and new electrode construction.
It is an object of the present invention to provide a miniature quartz crystal unit comprising a width-extensional mode quartz crystal resonator with a high electro-mechanical transformation efficiency.
It is an another object of the present invention to provide a miniature quartz crystal unit comprising a width-extensional mode quartz crystal resonator with a frequency higher than about 4 MHz with a small series resistance R1 and a high quality factor Q.
It is a further object of the present invention to provide a miniature quartz crystal unit comprising a width-extensional mode quartz crystal resonator with a zero temperature coefficient.
It is a still firer object of the present invention to provide a method of manufacturing a quartz crystal unit comprising a width-extensional mode quartz crystal resonator.
It is an another object of the present invention to provide a miniature quartz crystal oscillator comprising a width-extensional mode quartz crystal resonator with a high electro-mechanical transformation efficiency, a small series resistance R1, a high quality factor Q and a zero temperature coefficient.
In order to accomplish a miniature quartz crystal unit and a miniature quartz crystal oscillator comprising a width-extensional mode quartz crystal resonator with a frequency higher than about 4 MHz and a high electro-mechanical transformation efficiency by which a small series resistance R1 and a high quality factor Q are provided, it is needed to provide a novel width-extensional mode quartz crystal resonator which is formed from a quartz crystal plate with a new cutting angle, new electrode construction and a large piezoelectric constant.
In accordance with the present invention, the quartz crystal unit and the quartz crystal oscillator are accomplished by a width-extensional mode quartz crystal resonator with a new cutting angle and having new electrode construction and a large piezoelectric constant.
In more detail, such a resonator is formed in accordance with the present invention, from a quartz crystal plate of a new cutting angle using a particle method.
Moreover, such a resonator is provided in accordance with the present invention, by new electrode construction and a large piezoelectric constant.
In addition, in accordance with the present invention, a width-extensional mode quartz crystal resonator with a zero temperature coefficient is accomplished by a cutting angle. As a result of which a quartz crystal unit and a quartz crystal oscillator of the present invention comprising the width-extensional mode quartz crystal resonator have good frequency temperature behavior over a wide temperature range, respectively.